On my Arduino Uno platform I replaced the removable original Atmega 328 P-PU by a new one I bought separately from a platform.When I try to upload a program I get the message " not in sync". What should I do to upload my code?

One step at a time! Now I have bought a Standalone AVR ISP Programmer shield kit from Adafruit, I have soldered all the pieces to the board following the Arduino Hacks instructions (burning bootloader chips using an Arduino). I am now reaching the section " Load the code": when searching the Github link shown in the instructions I get :" 404, this is not the web page you are looking for". I am stuck here! Please let me know what I can do next.

Great,thanks, I got the Githud code, uploaded it to my Arduino Uno, plugged the shield over the Arduino, inserted the blank chip, clicked "burn bootloader". Then the process stopped. The error message is: " Expected signature for Atmega 328p is 1E950F Double check chip, or use -F to override this check"The red led on the shield is blinking; the yellow and green leds on the Arduino are lit.I need to be guided again!

I looked at the chips I bought from Digi-Key. They are Atmega 328P-PU. Furthermore, the blank chip I received from Adafruit with the shield kit ends up with the same problem.Thanks for bringing my attention to this detail.

This message is to Adafruit concerning order/invoice # 204391. At the same time I am trying to resolve a problem with my programmer shield, I have an other one with the two Atmega bootloader-programmed chips I bought from Adafruit:On my Arduino Uno platform I have a code which runs ok for my application. When I replace the original Atmega328P-PU by one that I bought, the code uploading does not complete. The error message is the same as when I use a blank Atmega: "not in sync".Thanks for your help.

On my Arduino Uno platform I have a code which runs ok for my application. When I replace the original Atmega328P-PU by one that I bought, the code uploading does not complete. The error message is the same as when I use a blank Atmega: "not in sync".

Are you still selecting UNO as the board type? Board type is dependent on the bootloader, not the name printed on the board. The pre-programmed bootloader on the chips we sell is the "Adaboot" loader. It uses the same protocol as the Duemilanove bootloader, so you must select "DUEMILANOVE with ATMEGA328" in the Arduino IDE.